1. Field of the Invention
The present invention relates to a new positive working photosensitive composition suitable for production of lithographic printing plates, proofs or multicolor printings, drawings for an overhead projector, integrated circuits, and photomasks.
2. Description of the Prior Art
o-Quinone diazide compounds have been known as so-called positive working photosensitive materials which are solubilized by activating rays. They have been widely used for lithographic printing plates, photoresists, etc. These o-quinone diazide compounds are described in many publications, for example, U.S. Pat. Nos. 2,766,118, 2,767,092, 2,772,972, 2,859,112, 2,907,665, 3,046,110, 3,046,111, 3,046,115, 3,046,118, 3,046,119, 3,046,120, 3,046,121, 3,046,122, 3,046,123, 3,061,430, 3,102,809, 3,106,465, 3,635,709 and 3,647,443.
The o-quinone diazide compounds are decomposed by irradiation with activating rays to become a five-membered carboxylic acid which is soluble in an alkali. However, they have a defect that their photosensitivity is yet insufficient, because the photochemical sensitization of them is difficult and their quantum yield does not essentially exceed 1. Further, the wave length for the sensitization usable is limited and, therefore, usable light sources are limited, namely the acceptability of light sources is much limited. Accordingly, it is difficult to use them in the light of an incandescent lamp for a long period of time (incandescent light safty lacks). Another problem is that their absorbance of a deep UV region of about 200 to 300 nm is high and therefore they are unsuitable when they are used to improve their resolving power with a light or low wave length.
Although various processes have been tried for improving the photosensitivity of a photosensitive composition containing an o-quinone diazide compound under these circumstances, it has been very difficult to improve the photosensitivity while the developability is kept good. These processes are described in, for example, Japanese Patent Publication for Opposition Purpose (hereinafter referred to as `J. P. KOKOKU`) No. 48-12242, Japanese Patent Unexamined Published Application (hereinafter referred to as `J. P. KOKAI`) No. 52-40125 and U.S. Pat. No. 4,307,173.
Recently, several positive working photosensitive compositions free of o-quinone diazide compounds have been proposed. Among them, proposed was a polymer compound having an o-nitrocarbinol ester group described in, for example, J. P. KOKOKU No. 56-2696. However, its photosensitivity is also yet insufficient for the same reasons as those of the o-quinone diazide compounds. Also, proposed is a compound which becomes sulfonic acid upon exposure as described in J. P. KOKAI Nos. 60-260947 and 62-36404. However, these compounds were not able to be easily produced.